I had a surging issue with my 1970 FLH. Spent a lot of time changing jets to help the issue, some seemed to help, others made it worse. Went on for a while, it was bad enough that my wife noticed it on a ride and wanted to know what was wrong with the bike. Different RPMs could make it go away, but then it would come right back on a shift. After 6 months, lots of time and effort, I give in and bring it to my Indy with a Dyno so we can get it sorted. He went through the same process with the the same results on the Dyno, he was stumped. Then he notices the rear chain was not in the best condition. He puts a new chain on the bike and it ALL goes away!!!

Not saying your chain is the issue, I guess I am just saying these bikes can be a PITA and it is not always what you think it is, good luck.

 

VERY interesting. Believe it or not, I already changed the plug wires. I learned that lesson the hard way on an older Ducati that I sold because I couldn't deal with the carb issues. New owner replaced the plug wires and it ran like new.

Never heard about a chain causing this issue - that one really stumps me, but I would believe anything at this point. The chain on this bike is brand new... all the sprockets.. actually every single part on this bike is new!

I'll try the main jet anyway, just for the hell of it. The only reason is because it does seem to be responding to the jetting changes....

 

Well for what it's worth, I went from the 66 main to 70, and it seems to be a tad worse. I may order a 68, or go back to the 66 for now. So far the bike seems to prefer a leaner main jet - but I'm still not convinced it's a jetting issue. I have on new plug wires.

I've been playing with the settings on this ignition - turning up a notch until I hear pinging, then backing off. Not sure what the VOES does? I am wondering if this could be part of the problem?

 

Never cared for that Compu-fire in a shovel. Try to get all the setting on it back basics and go from there.

 

If you're not using a VOES switch to monitor engine vacuum, Do not ground the green wire.. If you just tape it up and leave it like that it doesn't matter where you put the VOES switch setting on that model Compufire ignition.. It won't see a ground therefore it'll never advance.. Also I would use ignition curve setting number 6.. You shouldn't need more ignition than that in a stock motor..

 

Voes retards the timing when climbing a hill is the best way to explain it - then when you back off the throttle the timing comes back to full advance you chose in the over all set up - voes reduces the risk of pinging by retarding the timing by 10 degrees - it uses engine vacuum in the intake manifold to regulate

they came only on evo bikes but i have used them in FLT shovels lumber trucks - helps

your velocity is hi this makes the jetting work even harder - so you need leaner jetting to bring the. Tune in - 66 is around what is needed for a hi velocity engine

why - cam is too small for the compression your useing -BUT - it will pull hard - put. 50 miles on it and picture up the spark plugs so i can see if the jetting and heat range is correct — drive it like a human being till you get it right

 

HA! This is all very helpful. I just went down to a 68 main, but didn't ride it yet. I will put the 66 back in, and ride it like a human. Then post pics of the plugs...

Thanks for the VOES info, finally I'm starting to understand.

 

Hey John - I'm trying to find out exactly what cam we used, but I'm pretty sure it was a run of the mill Andrews evo type cam. I was looking more for longevity and reliability over performance. Also, I believe the compression is pretty standard.

Do you still think t I have hi velocity?

 

This is a thousand word conversation and 500 opinions first day - compression and camshaft ect ect ect - a pretty chick does not get that much input

once the computers came into play with automotive math instead of a pencil and seat of the pants involvement - it all changed

everyone now believes old ideas about duration is thing of the past - its lift stupid —- well maybe not

john andrews makes a usable cam for all around street riding and some YAHOO stuff but the engines dont last with yahoo - just as it starts to be fun they self destruct

the spark plugs will tell the story what your doing is right or over the top - put miles on it and picture them up

the plugs below is a customer pan head we have done a bunch of work on - the plugs are from this years riding it the color is what you after right is the front left is the rear its always a bit darker in its color - plus short plus the heat range is a bit harder to read but they are ne’er perfect as your going to get with the gas today

Yea the tin tops are seaping a bit reason the oil on the out side of the plugs - winter fix at this point

 

Rode 100 miles with the .031 intermediate, and 66 main. So far the best combination yet. The bike seems run better as the main jet gets smaller. The bike still sputters, but at higher RPM's. I'm also still getting some dieseling after I turn the bike off.

One more note - when we tried timing the bike with the timing gun, it was way off. Sounded and ran terribly. Using the static method timing (compu-fire instructions) it seems much better, but I suspect it's still a little off.

Shall I try dropping down to a 64 main?